Field of the Invention
The present invention relates to a combustion engine air intake system of a motorcycle provided with a supercharger which is driven by power of a combustion engine and which compresses intake air to be supplied to the combustion engine.
Description of Related Art
In order to enhance output of a combustion engine of a motorcycle, some combustion engines include a supercharger which pressurizes intake air (for example, WO2011/080974). The engine in WO2011/080974 includes a mechanical supercharger having therein a centrifugal type impeller which is driven by rotational force of a crankshaft of a combustion engine. In the motorcycle of WO2011/080974, in order to adjust the amount of intake air flowing into the supercharger, an intake air control valve is provided on the upstream side of the supercharger with respect to a flow direction of the intake air.
Since the weight of a motorcycle is relatively low, there are cases where a large change occurs in the rotation number of the combustion engine per unit time. This could cause delay in engine speed control effect obtained by changing the amount of intake air with the use of the intake air control valve. Specifically, when the intake air control valve is operated in a close direction to decrease the amount of intake air flowing into the supercharger, the fuel consumption reducing effect could be delayed due to delayed responsiveness to the decrease in the flow-in amount. When the intake air control valve is operated in an open direction to increase the amount of intake air flowing into the supercharger, increase of the output of the combustion engine could be delayed.